76 A REVISION OF THE ASTACID^. 



This species is unknown to me. Girard places it in his second group of 

 species (C. Bartonu and allies), with toothless rostrum and male appendages 

 recurved at their extremity. I am inclined to think that it is a Western 

 form of C. Dioffi'Hcs, or possibly C argillicola. Fort Pierre is on the right 

 bank of the Missouri River, at the mouth of Bad River, within the present 

 limits of the Territory of Dakota. Specimens of C. Diogenes collected at 

 Cheyenne, Wyoming, have the hand broad and fingers rather short, so that 

 the chela assumes a triangular shape when the fingers are closed. They 

 do not differ from G. D'mjenes enough to warrant a separation, but are 

 very likely the form named G. Nehrascensis by Girard. I do not know 

 what Hagen means when he says the hands resemble in shape those of 

 G. 3Iexicanus. 



28. Cambarus argillicola. 



Plato IV. flg. 3. 



Cambarus argillicola, Faxon, Proc. Amor. Acad. Arts and Sci., XX. 115, 1884. 



Rostrum .short, broad, down-curved, excavated, with a deep foveola at 

 base ; acumen short, broadly triangular, acute, no lateral spines. Post-orbital 

 ridges without anterior spines, swollen behind. Cephalothorax laterally 

 compressed, carapace punctate, anterior border not angulated, cervical 

 groove sinuate, no lateral or branchiostegian spine. Areola linear in the 

 middle, with an anterior and posterior triangular space, the latter the larger. 

 Abdomen broad, but narrow at the base, longer than the cephalothorax. 

 Telson uni- or bi-spinose on each side. Epistoma roimded in front. An- 

 tennal scale small, rounded within. Third maxillipeds heavily bearded 

 -within, lightly so beneath. Chela large, hand swollen, denticulate on inner 

 border, irregularly punctate, fingers flattened laterally, punctate and costate ; 

 the movable fino;er has a single row of tubercles on its external border and 

 a very prominent rib on its upiier face ; its internal, cutting edge is toothed 

 and excised at the base ; the outer finger is sharply marginate on its 

 external border, inner border toothed and heavily bearded at the base. 

 Carpus armed with a sharp spine and a few minute tubercles within ; be- 

 neath them is a sharp median anterior spine, and a minute spiniforin tubercle 

 between this and the spine of the internal border. Meros furnished with 

 one or two small subapical teeth on the superior border, and two rows of 

 teeth below. Second pair of legs ciliate near the end. Third pair of legs 



